<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title> "Stop the alert" 按钮</title>
</head>

<body>
    <p>点击第一个按钮等待3秒后出现"Hello"弹框。</p>
    <p>点击第二个按钮来阻止第一个函数运行。（你必须在3秒之前点击它）。</p>
    <button onclick="myFunction()">点我</button>
    <button onclick="myStopFunction()">停止弹框</button>
    <script>
        var myVar;
        function myFunction() {
            myVar = setTimeout(function () { alert("Hello") }, 3000);
        }
        function myStopFunction() {
            clearTimeout(myVar);
        }
    </script>
</body>

</html>